Measuring erythrocyte deformability with fluorescence, fluid forces, and optical trapping.

A laser-based method has been developed for experimentally probing single red blood cell (RBC) buckling and determining RBC membrane rigidity. Our method combines a liquid flow cell, fluorescence microscopy, and an optical-trap to facilitate simple measurements of the shear modulus and buckling properties of single RBCs, under physiological conditions. The efficacy of the method is illustrated by studying buckling behavior of normal and Plasmodium-infected RBCs, and the effect of Plasmodium falciparum-conditioned medium on normal, uninfected cells. Our simple method, which quantifies single-RBC deformability, may ease detection of RBC hematological disorders.